Undemanding, unsurprising and really quite charming within conventional limits, Elizabeth Allen’s tween-coming-of-age feature debut is as realist as can be, given that, of the three nice Florida girls who need to grow up in the movie, the eponymous heroine (Sara Paxton) is a high-achieving blond mermaid with vaguely feminist leanings, a twitchy blue tail and the comic timing of an up-and-coming Cameron Diaz.

A bright and breezy tween fantasy romantic comedy that coasts along on its charming performances and the light comedic touch of first-time feature director Elizabeth Allen.

Won't win points for originality, but the screenplay includes some snappy dialogue, smart observations, and an uplifting message about the importance of friendship.

Ms. Paxton isn't quite as magnetic as a movie mermaid ought to be, but the two buddies are a treat to watch, especially Ms. Roberts, showing the genes of her Aunt Julia.

That everything gets worked out -- friendship affirmed, jokes made about silly magazine articles on reeling in a boy -- is as sure as the soundtrack's inclusion of a Mandy Moore song.